The production of potatoes forms an important portion of the agriculture economy of the United States. Potatoes are used for both fresh vegetable markets, as well as value-added processed foods. For example, in the United States approximately 1.25 million acres of potatoes are planted each year. This acreage results in a farm-gate value of 3.06 billion dollars, according to the National Agricultural Statistician Service (NASS) of the U.S. Department of Agriculture (USDA), for year 2001. Within Washington State alone, approximately 160,000 acres of potatoes are grown annually for both domestic and international consumption. As in any industry, there exists a desire to increase productivity and efficiency in the process of taking a potato crop from a planting stage to a point-of-sale stage.
From the perspective of a grower or farmer, profitability is partly a function of crop yield, where crop output is maximized relative to input costs. Incentives are also an important part of profitability, where a grower is able to produce a crop meeting preset quality criteria. From a processing and packing perspective, final end product often defines the desired size and shape of raw product. For example, a french fry processor specializing in long, “steak”-cut style fries will want a uniform supply of 10 to 14 ounce potatoes. Likewise, a packer supplying fresh potatoes to restaurants for baking will want a uniform supply of 10 to 12 ounce potatoes with good skin quality. Extra costs are incurred when additional sorting, grading and transportation steps are required in order to meet the specific needs of particular processors and packers. Moreover, the additional handling of potatoes can decrease their quality due to bruising and other factors. Therefore, for the packer and processor, there are efficiencies to be gained by providing a potato production system that is specifically designed to deliver a specific end product. Furthermore, the commercial grower is also in a position to benefit financially by providing a raw product with higher market value. The same principles apply in the seed potato industry, where commercial growers desire receiving seed of uniform size and vigor from the seed grower. For example, the quality of seed has a great bearing on the performance and ultimate success of a potato crop.
A vast majority of acreage that is put into potato production each year in the U.S. is in geographic areas that require full or supplemental irrigation in order to meet crop water requirements. Current state-of-the-art in U.S. potato production uses center-pivot irrigation machines on large fields (typically over 60 acres), in order to make efficient use of farm equipment. Typically, potatoes are planted in a “hill” system where potato rows are separated by relatively deep furrows. These hills are typically spaced 34 or 36 inches apart depending on equipment conventions in the growing region.
Center-pivot irrigation is popular for several reasons. Much of the labor cost associated with irrigation is eliminated, center-pivot machines can be adapted to rolling and hilly ground and fertilizer and other products can be delivered in a metered manner through the irrigation water. However, there are disadvantages to center-pivot irrigation systems. One problem is that water is applied from overhead, potentially leading to excessively wet conditions within the crop canopy that tends to increase the potential for disease. Due to the intensity of the irrigation under a center-pivot irrigation device, there is also a tendency for the impact of water droplets to “beat down” the soil and canopy, which has a negative effect on plant health as well. Furthermore, there are limits as to how frequent an area within the irrigated field can receive needed moisture as it depends upon the traveling speed of the system. These factors do provide some challenges to growing an “above average” crop that suits many target markets.
In order to produce a high yielding crop that is uniform in size, shape and quality, there exist three primary requirements. First, there exists a need to provide for optimal plant spacing to take advantage of available field area and sunlight. Secondly, there exists a need to provide a uniform and favorable growing environment, such as a suitable amount of available soil moisture and nutrients. Finally, there exists a need to keep the plants healthy through maturity.
With a conventional hill planting system, there are severe limitations to providing optimal plant spacing. This is because the only variable that can be manipulated is the spacing of potato plants within a row. The spacing between rows is fixed due to the noted conventions in planting and harvest equipment. It follows that the grower is therefore unable to specifically and uniformly define the field area occupied by each plant. Research studies have shown that yield is directly related to cumulative intercepted sunlight energy by the plants. Therefore, it is important for the plant canopy (leaf area) to quickly and efficiently cover the field at an early stage in the season and, in doing so, it is also important that each potato plant “sees” the same amount of sunlight. A side-benefit of having early ground cover is the moderating effect the plant canopy has on temperatures within the canopy and in the soil, which is conducive to favorable and uniform growing conditions.
In consideration of the second requirement, the ability to “feed” or supply water and nutrients at the appropriate time and rate is fundamental to supporting steady plant growth and thereby producing a healthy, uniform crop. In achieving this end, there exists a need for a new, improved technique of drip irrigation that will provide a means by which water and nutrients can be delivered directly to the plant root zone according to the plant's needs. There is an additional need to provide for the delivery of moisture requirements below the soil surface, so that excessively wet conditions in the plant canopy can be avoided, thereby mitigating certain disease potential. Lastly, a system is needed that is capable of producing a high degree of uniformity of potato crop field-wide so that each plant is supplied equally with water and nutrients, including optional fertilizer.
FIG. 1 illustrates a prior art potato irrigation system that uses irrigation drip tape for irrigating beds 10, 12, and 14 of potatoes represented by seeds 20 having a maturing canopy 22. Seeds 20 are configured in rows 24, 26, 28, and 30. An irrigation drip tape 32 is provided between the two center rows 26 and 28 of each bed 10, 12, and 14. The outer rows 24 and 30 are not optimally irrigated by tape 32 because they are spaced apart from tape 32 an unacceptable distance which means that outer rows are under-watered (or inner rows are over-watered).
The system of FIG. 1 represents seed potato production at a known location in France using drip irrigation. A soil surface view of the beds is shown. Seed spacing was 9.7 inches along each row, with four lines on a 71-inch bed. Plant population was 36,437 plants/acre.
FIG. 2 illustrates a sub-surface view taken just above the irrigation drip tape within beds 10, 12, and 14. Emitters 34 are shown spaced along each tape 32. The inefficient placement of emitters 34 places many seeds (and plant root systems) too far from emitters 34 to optimize plant production and effectively reduce disease.
The system and method of potato production presented herein gives a grower an advantage in meeting the above-identified deficiencies.